Twin Eco Heat Pumps have been installed to supply energy efficient heating and hot water for a new Community Centre in the Western Isles.
The committee responsible for converting the old primary school at Shawbost on the Isle of Lewis into a multi-purpose centre was keen to incorporate renewable energy systems and therefore Eco Heat Pumps of Sheffield developed a geo-thermal system based on two Thermia Robust 28 units with a combined capacity of 58kW.
Heat is drawn into the system from deep below the ground surface. A water-glycol mixture is pumped through pipework in a dozen 75 metre boreholes. At this depth in the Lewis Gneiss layer – the UK’s oldest rock formation – temperatures average 9oC. This naturally occurring heat is used to raise the temperature of the water returning to the heat pumps. Here the action of the compressors and condensers in the Eco units brings the water temperature up to the levels required by the space heating and domestic hot water systems.
The new Centre at Shawbost performs a wide ranging role with facilities for both community and commercial activities. The stage and gymnasium areas can also be used for public or private meetings, while other needs can be met by the nursery, the library and the Internet café.
Eco’s heat pump system serves all areas of the Centre supplying hot water to both the underfloor heating and radiator systems. Ample supplies of domestic hot water are available at all times.
The system is weather compensated with external and flow temperature sensors modulating operation of the heat pumps to maintain the target temperature. COP for the space heating system has been calculated at 4.2:1 and for the dhw supply as 2.8:1.
At the moment electricity to power the system is drawn from the mains grid on a green tariff. Future plans include the installation of a wind turbine to supply electricity to the Centre.